feat: material.blend_method migration for EEVEE-Next

src/io_scene_vrm/common/native.py

@@ -0,0 +1,91 @@
+import ctypes
+import sysconfig
+from collections.abc import Mapping
+from platform import python_implementation
+from typing import Optional
+
+import bpy
+from bpy.types import Material
+
+from .logging import get_logger
+
+logger = get_logger(__name__)
+
+
+def read_blend_method_from_memory_address(material: Material) -> Optional[str]:
+    """material.blend_methodの値を直接メモリから読み取る.
+
+    Blender 4.2からmaterial.blend_methodの値が廃止されて読めなくなった。
+    しかし、マテリアルのマイグレーションのためにはどうしてもその値を知る必要がある。
+
+    仕方がないので既知のプラットフォームに限定してメモリから直接値を読む。
+    ログは多めに出す。
+    """
+    if bpy.app.version < (4, 2):
+        return material.blend_method
+
+    if bpy.app.build_type != b"Release":
+        logger.warning(
+            f"Does not read the Blend Mode of {material.name}. "
+            + f'"{bpy.app.build_type!r}" builds are not supported.'
+        )
+        return None
+
+    if python_implementation() != "CPython":
+        logger.warning(
+            f"Does not read the Blend Mode of {material.name}. "
+            + f"{python_implementation()} is not supported."
+        )
+        return None
+
+    native_struct_offsets_by_major_minor: Mapping[
+        tuple[int, int],
+        Mapping[str, int],
+    ] = {
+        (4, 2): {
+            "win-amd64": 324,
+            "macosx-11.00-arm64": 324,
+        },
+    }
+
+    major_minor = (  # Use [x] to make type checkers happy
+        bpy.app.version[0],
+        bpy.app.version[1],
+    )
+    native_struct_offsets = native_struct_offsets_by_major_minor.get(major_minor)
+    if native_struct_offsets is None:
+        logger.warning(
+            f"Does not read the Blend Mode of {material.name}. "
+            + f"Blender {major_minor[0]}.{major_minor[1]} is not supported."
+        )
+        return None
+
+    platform = sysconfig.get_platform()
+    native_struct_offset = native_struct_offsets.get(platform)
+    if native_struct_offset is None:
+        logger.warning(
+            f"Does not read the Blend Mode of {material.name}. "
+            + f"{platform} is not supported."
+        )
+        return None
+
+    logger.warning(
+        f"Starts reading the Blend Mode of {material.name} from its memory address."
+    )
+    native_char = ctypes.c_char.from_address(
+        material.as_pointer() + native_struct_offset
+    )
+    logger.warning(
+        f"Finished reading the Blend Mode of {material.name} from its memory address."
+    )
+
+    if native_char.value == bytes([0]):
+        return "OPAQUE"
+    if native_char.value == bytes([3]):
+        return "CLIP"
+    if native_char.value == bytes([4]):
+        return "HASHED"
+    if native_char.value == bytes([5]):
+        return "BLEND"
+
+    return None

src/io_scene_vrm/editor/mtoon1/migration.py

@@ -10,7 +10,7 @@
 )
 from idprop.types import IDPropertyGroup
 
-from ...common import convert
+from ...common import convert, native
 from ...common.gl import GL_LINEAR, GL_NEAREST
 from .property_group import (
     GL_LINEAR_IMAGE_INTERPOLATIONS,
@@ -92,9 +92,10 @@ def migrate(context: Context) -> None:
         alpha_cutoff: Optional[float] = None
         if addon_version < (2, 20, 55):
             alpha_cutoff = material.alpha_threshold
-            if material.blend_method in ["BLEND", "HASHED"]:
+            blend_method = native.read_blend_method_from_memory_address(material)
+            if blend_method in ["BLEND", "HASHED"]:
                 alpha_mode = Mtoon1MaterialPropertyGroup.ALPHA_MODE_BLEND
-            if material.blend_method == "CLIP":
+            if blend_method == "CLIP":
                 alpha_mode = Mtoon1MaterialPropertyGroup.ALPHA_MODE_MASK
             else:
                 alpha_mode = Mtoon1MaterialPropertyGroup.ALPHA_MODE_OPAQUE

tests/blender_test_read_blend_method_from_memory_address.py

@@ -0,0 +1,27 @@
+from pathlib import Path
+
+import bpy
+from bpy.types import Context
+
+from io_scene_vrm.common.native import read_blend_method_from_memory_address
+
+
+def test(context: Context) -> None:
+    bpy.ops.wm.open_mainfile(filepath=str(Path(__file__).parent / "blend_mode.blend"))
+
+    for material_name, expected_blend_method in {
+        "Opaque": "OPAQUE",
+        "AlphaClip": "CLIP",
+        "AlphaHashed": "HASHED",
+        "AlphaBlend": "BLEND",
+    }.items():
+        material = context.blend_data.materials[material_name]
+        actual_blend_method = read_blend_method_from_memory_address(material)
+        assert expected_blend_method == actual_blend_method, (
+            f'"{material_name}" material is not "{expected_blend_method}"'
+            + f" but {actual_blend_method}"
+        )
+
+
+if __name__ == "__main__":
+    test(bpy.context)